High-frequency Link Matrix Converter Research Articles

A Novel SVM Strategy to Reduce Current Stress of High-Frequency Link Matrix Converter

High-frequency link matrix converter (HFLMC) can directly realize DC/AC conversion without intermediate energy storage components, reduce the power conversion stage, and improve efficiency and power density. With the conventional space vector modulation strategy, the secondary side voltage of the high-frequency transformer presents an asymmetric trapezoidal wave, which leads to the DC magnetic bias phenomenon and increases the current stress in secondary side switches. This paper proposes a novel SVM strategy for HFLMC. It optimizes the space vector distribution, makes secondary side voltage periodic and symmetric, and reduces the switching actions. The current stress is reduced, and the converter's efficiency is improved. Simulation and experiment results verify the advantages of the proposed modulation strategy.

Dynamic Performance Improvement of Continuous Control Set Model Predictive Control for High-Frequency Link Matrix Converter

In this paper, a comprehensive control strategy of a high frequency link matrix converter (HFLMC) based on the interaction technology between electric vehicle and power grid is proposed to improve the dynamic performance of the system. The continuous control set model predictive control (CCS-MPC) is applied to the current loop to solve the problems of difficult selection of PI control parameters and slow dynamic response speed. In order to ensure that the grid-connected current can achieve better command tracking, a deviation suppression term is introduced into the cost function of CCS-MPC, and the online auto tuning method of weight factors of fast-tracking term and deviation suppression term is designed. On this basis, the PWM signals are generated by the coordinated modulation strategy of the HFLMC to obtain a constant switching frequency, which makes the harmonic of the grid connected current easier to be filtered out. Experimental results show the correctness and feasibility of the proposed control strategy.

A Modified Space Vector Modulation for DC-Side Current Ripple Reduction in High-Frequency Link Matrix Converter

A high-frequency link matrix converter (HFLMC) has been increasingly used in power conversion for its distinct advantages of high efficiency and compact volume. However, the conventional six-segment space vector PWM (SVPWM) scheme leads to high current ripple on the dc side and distortion on the ac side, which can inevitably destroy the battery load and decrease power quality. This article proposes a modified SVPWM scheme with dwell time and sequence compensation (MC-SVPWM) to reduce the current ripple and distortion under high modulation index conditions. The proposed MC-SVPWM allocates the vector sequence and adjusts the duration of the vector, simultaneously. First, the reasons for the current ripple and distortion under the conventional six-segment SVPWM (6S-SVPWM) scheme are analyzed in detail. The relationship between the vector duration and the dc-side current ripple is revealed. Then, the derivation process of the proposed MC-SVPWM scheme is introduced. Compared with the conventional 6S-SVPWM scheme, the dc-side current ripple is decreased greatly, and the ac-side current distortion is reduced consequently under the proposed MC-SVPWM scheme. Simulation and experimental results verify the effectiveness of the proposed modulation strategy.

Power Sharing Control Strategy of High-Frequency Chain Matrix Converter Parallel System Based on Adaptive Virtual Impedance

In the high frequency link matrix converter parallel system, the impedance parameters on each line are unequal so that the output power of each converter is not equal. To solve this problem, the reason why the power cannot be divided equally under the droop control strategy is analyzed, and a power sharing strategy based on adaptive virtual impedance is proposed. This strategy introduces virtual impedance in a voltage-current dual-loop system with droop control, and uses the converter’s power information and output power factor to adaptively adjust the amplitude and phase of the virtual impedance, so that different branches have the same equivalent output impedance to compensate The voltage drop on the line impedance, while adding the droop control fine-tuning compensation link, so as to realize the load power sharing. Simulation results show that the proposed strategy can effectively improve the accuracy of output power sharing and ensure the stability of the system output voltage amplitude.

A Novel Carrier-Based PWM Without Narrow Pulses Applying to High-Frequency Link Matrix Converter

In order to eliminate narrow pulses completely, this paper presents a novel carrier-based pulse width modulation (CBPWM) strategy applying to high-frequency link matrix converter (HFL-MC). Following the De-Re-couple idea, a single-phase to three-phase MC is equivalent to two full-bridge inverters according to the polarity of input voltage. The voltage of switches in two full-bridge inverters is analyzed and derived the duty cycles of switches according to the relationship between the state and the voltage of the switch. The duty cycles of three phases in the two inverters are integrated into a unified expression to generate the final modulation waves. A dual modulation strategy is proposed to compare modulation waves and a triangular carrier, which can achieve almost constant duty cycle of gating signals regardless of output voltage change. Therefore, the narrow pulses are eliminated fundamentally. Finally, the experimental results are given to show the advantages and the effectiveness of the proposed modulation strategy.

EMI Filter Design for a Single-stage Bidirectional and Isolated AC–DC Matrix Converter

This paper describes the design of an electromagnetic interference (EMI) filter for the high-frequency link matrix converter (HFLMC). The proposed method aims to systematize the design process for pre-compliance with CISPR 11 Class B standard in the frequency range 150 kHz to 30 MHz. This approach can be extended to other current source converters which allows time-savings during the project of the filter. Conducted emissions are estimated through extended simulation and take into account the effect of the measurement apparatus. Differential-mode (DM) and common-mode (CM) filtering stages are projected separately and then integrated in a synergistic way in a single PCB to reduce volume and weight. A prototype of the filter was constructed and tested in the laboratory. Experimental results with the characterization of the insertion losses following the CISPR 17 standard are provided. The attenuation capability of the filter was demonstrated in the final part of the paper.

Modulation Strategy for a Single-Stage Bidirectional and Isolated AC–DC Matrix Converter for Energy Storage Systems

This paper presents a new modulation and control strategies for the high-frequency link matrix converter (HFLMC). The proposed method aims to achieve controllable power factor in the grid interface as well as voltage and current regulation for a battery energy storage device. The matrix converter (MC) is a key element of the system, since it performs a direct ac to ac conversion between the grid and the power transformer, dispensing the traditional dc-link capacitors. Therefore, the circuit volume and weight are reduced and a longer service life is expected when compared with the existing technical solutions. A prototype was built to validate the mathematical analysis and the simulation results. Experimental tests developed in this paper show the capability of controling the grid currents in the synchronous reference frame in order to provide grid services. Simultaneously, the battery current is well regulated with small ripple, which makes this converter ideal for battery charging of electric vehicles and energy storage applications.

An Integration SPWM Strategy for High-Frequency Link Matrix Converter With Adaptive Commutation in One Step Based on De-Re-Coupling Idea

When matrix converter (MC) and high-frequency link (HFL) are combined together, they become more complex and gain a safe commutation for the use of high-frequency transformer. To realize energy conversion and transmission, and to achieve reliable and safe commutation at the same time are particularly important and desirable. HFL matrix converter (HFLMC) can be divided into two types: high-frequency link matrix inverter (HFLMI) and high-frequency link matrix rectifier (HFLMR). A three-phase output HFLMI is selected as the object of this study, and a novel integration sinusoidal pulse width modulation (SPWM) control strategy with one-step adaptive commutation based on De-Re-coupling idea is proposed for it. After expounding on the De-Re-coupling idea, a kind of HFLMC equivalent circuit model based on the high-frequency transformer equivalent circuit is built up. Then, a detailed analysis of the voltage stress on power devices of the HFLMC by using this model is performed. A safe operation evaluation criterion of HFLMC is also gained. A suggestion of how to select carrier wave for integration SPWM is ascertained through detail discussion, and two kinds of specific Re-coupling logic circuits are presented, and at last some experimental results are shown to make a certification for feasibility and effectiveness of the new proposed SPWM strategy.